looks like you are on there right track. if you have the TJ springs or can get them cheaper or something then you can use them and a little spacers (`1")to get 3" in the front and move your front springs to the back to net 3" all around. be aware this means you need new shocks, track bars, and sway bar links in the front. also, you need to make sure you have a ujoint front driveshaft (no rubber boot at diff) or swap one on.
'98 ZJ on 37s and tons
'02 Chevy 2500HD 8.1